Rotational Spectra of Four of the Five Conformers of 1-Pentene

Published

April 1, 2000

Author(s)

Gerald T. Fraser, L H. Xu, R D. Suenram, C Lugez

Abstract

The rotational spectra of four of the five expected conformers of 1-pentene, together with their monosubstituted ¹³C isotopic forms, have been measured in a molecular beam using a pulsed-nozzle Fourier-transform microwave spectrometer. One of the conformers has C_s point-group symmetry while the other three conformers have C₁ point-group symmetry. The measurements are compared to results from molecular modeling calculations using the MM3 molecular-mechanics force field of Allinger et al. and to ab initio electronic structure calculations (MP2/6-31G*, MP2/6-311G*, MP4/6-31G*, MP4/6-311G*). Both types of calculations suggest the existence of five distinct conformers of 1-pentene, 4 of C₁ symmetry and 1 of C_s symmetry. Both the MM3 and ab initio rotational constants deviate from the measured values by {less then or equal to} 5 %. The relatively high barriers between the four conformers limit the conformational cooling in the expansion, allowing all four conformers to be observed at the

Citation

Journal of Chemical Physics

Volume

112

Issue

No. 14

Pub Type

Journals

Keywords

alkene, conformation, intermolecular forces, internal rotation, microwave spectroscopy, pentene

Citation

Fraser, G. , Xu, L. , Suenram, R. and Lugez, C. (2000), Rotational Spectra of Four of the Five Conformers of 1-Pentene, Journal of Chemical Physics (Accessed May 10, 2025)